Protective layer on slope of moles and breakwaters



Oct. 12, 1965 H. R. SVEE 3,210,944

PROTECTIVE LAYER ON SLOPE 0F MOLES AND BREAKWATERS Filed Nov. 9. 1962 UINVENTOR HALL BJORN ROALD SVEE United States Patent 3 Claims. c1. 61-4)The present invention relates to blocks for making protecting layers onslopes of moles and breakwaters exposed to water in motion.Constructions of this kind often have slopes which are exposed to verylarge wave attack. The outer protecting layer forming a surface of theslope, therefore, consists of blocks or stones of large dimensions. Itis sometimes necessary to produce these blocks artificially because itis not always possible to find stones of suitable dimensions in theneighborhood of the building spot or in a stone quarry in a suitableposition.

In recent times blocks have often been used for forming such protectinglayers. These blocks are constructed in such way that certain spaces oropenings between neighboring blocks are obtained, and at the same timethe center of gravity of every single block is low to prevent the blocksfrom turning over. This is obtained by providing the blocks withprotrusions of different kinds, such as short frusto-conical arms which,in certain embodiments, point out in different directions from a centercore. Thereby is also obtained that the blocks are prevented fromsliding along the inclined stone base of the slope, or one upon theother if the blocks are laid out in several layers. In order to furtherimpede the sliding along the slope such known blocks are made with asfew plane surfaces as possible.

By making the blocks in this way they are prevented from being moved inthe direction which has, until now, been regarded as the decisive one,namely, up and down along the slope. However, calculations andlaboratory tests, which have recently been carried out (see Roald Svee:Formulas for Design of Rubble-Mound Breakwaters, Journal of theWaterways and Harbors Division, Proceedings of the American Society ofCivil Engineers, Vol. 88, No. WW2, May 1962) show that a movementsubstantially at right angles to the slope is of greater importance tothe stability of the protecting cover than the movement along the slope.For this reason the blocks should, first of all, be prevented from beingmoved in a direction normal to the slope. The spaces which are obtainedbetween the known blocks due to their form more or less prevent themfrom holding each other in place and, for this reason, there arepreferably used two layers laid out in a special way and with a certainaccuracy to obtain an interlocking in the said direction at right anglesto the slope. If these known blocks are laid out in one layer only it ispractically impossible to obtain an interlocking effect which will haveany influence in the decisive direction.

It is also previously known to make protecting covers for moles andbreakwaters from blocks which more or less engage each other, so thateach single block will contribute to keep the other blocks in placeagainst the lifting force of the water. However, blocks of this type arenot able to withstand the forces created by large waves since thepressure difference between the upper and lower side of the blocks willbe of such magnitude that the cover is disrupted. A certain improvementmay be obtained if the base on which the blocks are resting, consists oflarge stones or is provided with channels for leading away the waterwhich flows back, but neither of these 3,210,944 Patented Oct. 12, 1965"ice precautions have been found sufiicient when the waves are large.

It is also known to make use of blocks which have through-going openingsin direction normal to the base in order to reduce the pressuredifference, but this precaution is also insufficient when the mole orbreakwater is subjected to large water forces.

The object of the present invention is to arrive at a block for formingprotective layers on slopes of moles and breakwaters and, according tothe invention, this is obtained by forming each block in such way thatof its sides facing the neighboring blocks at least one is made forinterlocking with one of the neighboring blocks so that the blocks willprevent one another from moving in a direction up from the slope, and insuch way that the cover made from the blocks will have at least onethroughgoing opening per block from the waterside to the surface restingon the slope so that the pressure and suction forces to which the blocksare subjected due to the movement of the water are reduced.

By combining these two features as known per se it has surprisingly beenfound that it is possible to form a protective cover which willwithstand waves of more than the double height as compared with blockshaving only one or the other of the known features, which result isobtained by a weight of the cover of about the half of that of coversmade from the hitherto known blocks.

On the water side the blocks are preferably provided with upwardlydirected protrusions serving to break the force of the waves and to,simultaneously, obstruct large uprush of the water.

The invention is now to be described with reference to the drawing inwhich:

FIG. 1 shows a section of a mole or breakwater with a protecting coverconsisting of cast blocks according to the invention,

FIG. 2 shows a block in larger scale and in perspective formed forinterlocking with the upper and lower blocks,

FIG. 3 shows a block, also in perspective, made for interlocking withthe upper and lower blocks and with the other neighboring blocks aswell, and

FIG. 4 shows a block, also in perspective, having recesses in its sidewalls.

The mole or breakwater 1 shown in cross section in FIG. 1 has two slopes1a and 1b, of which the first mentioned is directed against theuprushing Waves (the water side), and which is, therefore, provided witha protecting cover made from cast concrete blocks 2, the lower surfaces3 of which rest on the slope 1a. The lowermost block is kept in place bystones 9, and the surface of it facing the next upper block is made witha rib or protrusion 6', 6a (see also FIG. 2) which engages acorrespondingly shaped recess 6, 6a in the lower side of the said uppernext block. Since all the blocks 2 are equal they will, as seen indirection down the slope, be in engagement with the respective upper andlower blocks. At the top the mole or breakwater has a cast head or crest8 of substantially angular cross section, the upright leg of whichengages the uppermost block.

As appears especially from FIG. 2, the block 2 is defined by a flatlower resting surface 3, two vertical and mutually parallel sidesurfaces 7 and 7', and at right angles to same, mutually parallel andinclined upwardly directed surfaces 6 and 6 which continue in two oppositely inclined, also mutually parallel surfaces 6a and 6a. The topsurface 4 of the block forms an acute angle with bottom surface 3 sothat there will be an inclined, upwardly directed cam or rib 6c, thesection of which has the form of a saw tooth. This upper portion 60 islocated above plane 617 which is parallel to the bottom surface 3.Between the upper and lower surfaces 3 and 4 there are arrangedthrough-going openings 5, in the shown example two such openings.

It is obvious, as FIG. 4 shows, that each block may be formed witheither openings 5, as shown, or with recesses 5a in its side walls, orboth, so that two such recesses 5a will together define a through-goingopening between the neghboring blocks, preferable in addition toopenings 5.

A cover for the water side of a mole or breakwater built up from blocksaccording to FIG. 2 will Withstand high waves which is due to thecombination of the features that the blocks are in engagement with eachother, at least in the vertical direction, and that the blocks areprovided with through-going openings. A wave rushing up along the slopewill not act with the same force upon all the blocks simultaneously.That block which is at a certain moment subjected to the largest liftingforce caused by one wave will, therefore, be kept in place by the upperand lower blocks. At the same time the openings 5 and also the spacesbetween the blocks will act to reduce the suction force upon the blockcaused by the waves.

As appears from FIG. 1, the protecting cover will have a saw bladeformed cross section, so as to impede the uprush of the waves and breakat least a part of the living force of same. This feature in combinationwith both the above mentioned features will give a protective coverwhich will withstand very large waves without the blocks being displacedin any direction. It is to be observed that this advantage is obtainedin connection with a layer of a substantially low weight, which is ofspecial importance when the blocks have to be produced at one place andtransported to the mole or breakwater to be provided with a protectivelayer.

The form of the blocks as shown in the drawing also brings with it theadvantage that the blocks may easily be slid in place along the slope1a. This facilitates the laying work and the later maintenance of thecover. If, for instance, the lowermost block should for some reasonslide away, a new block may be placed at the top and slid down so as tocover the opening thereby formed.

FIG. 3 shows a block similar to FIG. 2 and modified so that it will alsoengage the neighboring blocks in the horizontal direction, there beingin addition to the upper protrusions and lower recesses also arranged aprotrusion and a recess respectively in the two side faces 7 and 7'. Themiddle portions 6d and 6d of the upper and lower surfaces respectivelyare in this embodiment perpendicular to the bottom surface 3 but theymay also be formed according to FIG. 2. According to FIG. 3 this blockis defined by the following surfaces: A plane bottom surface 3, twoinclined and mutually parallel surfaces 6 and 6, two vertical, mutuallyparallel surfaces 6d and 6d, two inclined surfaces 6a and 6a, of whichthe first continues in the surface forming the short face of the rib 6cdirected against the waves. The other sides of the block are defined bymutually parallel surfaces 7b, 7b and 7a, 7a respectively with twointermediate and mutually parallel, inclined surfaces 7d, 7d and 7c, 70'respectively forming a protrusion in one side and a correspondinglyshaped recess in the other side. Also in this case it is possible toslide the blocks in place along the slope.

In this embodiment also an interlocking between the neighboring blocksin the sidely direction is obtained so that the protecting cover will beable to withstand still higher waves than a cover built up from blocksaccording to FIG. 2. However, it will be obvious that the interlockingbetween the blocks in the vertical direction will be of greaterimportance for the stability of the cover than that between the blocksin the horizontal direction, since substantially all the blocks in thesame height will be subjected to the same lifting force when a wave isrushing up the slope.

I claim:

1. A protective layer for the slope of a mole, breakwater or the likecomprising a plurality of blocks arranged in inclined rows andhorizontal rows on a slope, each of said blocks having a top surface, abottom surface lying against said slope in an inclined plane common toother of said blocks, a pair of laterally facing sides, an upwardlyfacing side and a downwardly facing side, said top surface of each blocklying in a plane which intersects at an acute angle the inclined planein which said bottom surface lies so that an edge defined by said topsurface and said downwardly facing side is a greater distance from saidslope than an edge defined by said top surface and said upwardly facingside, said first named edge of each block in adjacent ones of saidhorizontal rows being vertically disposed above and with its down wardlyfacing side overhanging the top surface of a block in the horizontal rownext below, each of said blocks having interlocking means provided onsaid upwardly facing and downwardly facing sides thereof, said means ofthe block of adjacent one of said horizontal rows being interlocked toprevent the blocks from moving in a direction away from said slope underthe force of Waves, and each block having a passageway extendingtherethrough from its bottom to its top surface for reducing pressureand suction forces to which said layer is subjected due to movement ofwaves thereon.

2. A protective layer according to claim 1 wherein each of said blockshas interlocking means provided on said pair of laterally facing sides,said latter means interlocking each block with an adjacent block in itshorizontal row.

3. A protective layer according to claim 1 wherein each of said blockshas said passageway formed in a side of said pair of laterally facingsides.

References Cited by the Examiner UNITED STATES PATENTS 3,091,087 5/63Danel 6137 X FOREIGN PATENTS 546,700 4/56 Belgium. 1,019,630 11/52France. 1,242,856 8/60 France.

667,512 3/52 Great Britain. 795,349 5/58 Great Britain. 951,372 3/ 64Great Britain.

92,988 12/59 Holland.

EARL J. WITMER, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

1. A PROTECTIVE LAYER FOR THE SLOPE OF A MOLE, BREAKWATER OR THE LIKECOMPRISING A PLURALITY OF BLOCKS ARRANGED IN INCLINED ROWS ANDHORIZONTAL ROWS ON A SLOPE, EACH OF SAID BLOCKS HAVING A TOP SURFACE, ABOTTOM SURFACE LYING AGAINST SAID SLOPE IN AN INCLINED PLANE COMMON TOOTHER OF SAID BLOCKS, A PAIR OF LATERALLY FACING SIDES, AN UPWARDLYFACING SIDE AND A DOWNWARDLY FACING SIDE, SAID TOP SURFACE OF EACH BLOCKLYING IN A PLANE WHICH INTERSECTS AT AN ACUTE ANGLE THE INCLINED PLANEIN WHICH SAID BOTTOM SURFACE LIES SO THAT AN EDGE DEFINED BY SAID TOPSURFACE AND SAID DOWNWARDLY FACING SIDE IS A GREATER DISTANCE FROM SAIDSLOPE THAN AN EDGE DEFINED BY SAID TOP SURFACE AND SAID UPWARDLY FACINGSIDE, SAID FIRST NAMED EDGE OF EACH BLOCK IN ADJACENT ONES OF SAIDHORIZONTAL ROWA BEING VERTICALLY DISPOSED ABOVE AND WITH ITS DOWNWARDLYFACING SIDE OVERHANGING THE TTOP SURFACE OF A BLOCK IN THE HORIZONTALROW NEXT BELOW, EACH OF SAID BLOCKS HAVING INTERLOCKING MEANS PROVIDEDON SAID UPWARDLY FACING AND DOWNWARDLY FACING SIDES THEREOF, SAID MEANSOF THE BLOCK OF ADJACENT ONE OF SAID HORIZONTAL ROWS BEING INTERLOCKEDTO PREVENT THE BLOCKS FROM MOVING IN A DIRECTION AWAY FROM SAID SLOPEUNDER THE FORCE OF WAVES, AND EACH BLOCK HAVING A PASSAGEWAY EXTENDINGTHERETHROUGH FROM ITS BOTTOM TO ITS TTOP SURFACE FOR REDUCING PRESSUREAND SUCTION FORCES TO WHICH SAID LAYER IS SUBJECTED DUE TO MOVEMENT OFWAVES THEREON.